安卓颜色，最快？

Question

什么是更快的安卓？

Color.rgb(184, 134, 011);

或

Color.parseColor("#234181");

还是别的什么？

答案:最快的似乎是:

int mycolor = 0xff234181;

感谢 samgak 和 KenWolf。

但是现在我想知道常用函数是如何处理它的，这里是 2 View setbackgroundcolor() 和 TextView settextcolor() 和(一些)以下函数的来源:

public void setBackgroundColor(int color) {
    if (mBackground instanceof ColorDrawable) {
        ((ColorDrawable) mBackground.mutate()).setColor(color);
        computeOpaqueFlags();
        mBackgroundResource = 0;
    } else {
        setBackground(new ColorDrawable(color));
    }
}

public void setBackground(Drawable background) {
    //noinspection deprecation
    setBackgroundDrawable(background);
}

public void setBackgroundDrawable(Drawable background) {
    computeOpaqueFlags();

    if (background == mBackground) {
        return;
    }

    boolean requestLayout = false;

    mBackgroundResource = 0;

    /*
     * Regardless of whether we're setting a new background or not, we want
     * to clear the previous drawable.
     */
    if (mBackground != null) {
        mBackground.setCallback(null);
        unscheduleDrawable(mBackground);
    }

    if (background != null) {
        Rect padding = sThreadLocal.get();
        if (padding == null) {
            padding = new Rect();
            sThreadLocal.set(padding);
        }
        resetResolvedDrawables();
        background.setLayoutDirection(getLayoutDirection());
        if (background.getPadding(padding)) {
            resetResolvedPadding();
            switch (background.getLayoutDirection()) {
                case LAYOUT_DIRECTION_RTL:
                    mUserPaddingLeftInitial = padding.right;
                    mUserPaddingRightInitial = padding.left;
                    internalSetPadding(padding.right, padding.top, padding.left, padding.bottom);
                    break;
                case LAYOUT_DIRECTION_LTR:
                default:
                    mUserPaddingLeftInitial = padding.left;
                    mUserPaddingRightInitial = padding.right;
                    internalSetPadding(padding.left, padding.top, padding.right, padding.bottom);
            }
            mLeftPaddingDefined = false;
            mRightPaddingDefined = false;
        }

        // Compare the minimum sizes of the old Drawable and the new.  If there isn't an old or
        // if it has a different minimum size, we should layout again
        if (mBackground == null
                || mBackground.getMinimumHeight() != background.getMinimumHeight()
                || mBackground.getMinimumWidth() != background.getMinimumWidth()) {
            requestLayout = true;
        }

        background.setCallback(this);
        if (background.isStateful()) {
            background.setState(getDrawableState());
        }
        background.setVisible(getVisibility() == VISIBLE, false);
        mBackground = background;

        applyBackgroundTint();

        if ((mPrivateFlags & PFLAG_SKIP_DRAW) != 0) {
            mPrivateFlags &= ~PFLAG_SKIP_DRAW;
            mPrivateFlags |= PFLAG_ONLY_DRAWS_BACKGROUND;
            requestLayout = true;
        }
    } else {
        /* Remove the background */
        mBackground = null;

        if ((mPrivateFlags & PFLAG_ONLY_DRAWS_BACKGROUND) != 0) {
            /*
             * This view ONLY drew the background before and we're removing
             * the background, so now it won't draw anything
             * (hence we SKIP_DRAW)
             */
            mPrivateFlags &= ~PFLAG_ONLY_DRAWS_BACKGROUND;
            mPrivateFlags |= PFLAG_SKIP_DRAW;
        }

        /*
         * When the background is set, we try to apply its padding to this
         * View. When the background is removed, we don't touch this View's
         * padding. This is noted in the Javadocs. Hence, we don't need to
         * requestLayout(), the invalidate() below is sufficient.
         */

        // The old background's minimum size could have affected this
        // View's layout, so let's requestLayout
        requestLayout = true;
    }

    computeOpaqueFlags();

    if (requestLayout) {
        requestLayout();
    }

    mBackgroundSizeChanged = true;
    invalidate(true);
}

和

public void setTextColor(int color) {
mTextColor = ColorStateList.valueOf(color);
    updateTextColors();
}

public void setTextColor(ColorStateList colors) {
    if (colors == null) {
        throw new NullPointerException();
    }

    mTextColor = colors;
    updateTextColors();
}

private void updateTextColors() {
    boolean inval = false;
    int color = mTextColor.getColorForState(getDrawableState(), 0);
    if (color != mCurTextColor) {
        mCurTextColor = color;
        inval = true;
    }
    if (mLinkTextColor != null) {
        color = mLinkTextColor.getColorForState(getDrawableState(), 0);
        if (color != mTextPaint.linkColor) {
            mTextPaint.linkColor = color;
            inval = true;
        }
    }
    if (mHintTextColor != null) {
        color = mHintTextColor.getColorForState(getDrawableState(), 0);
        if (color != mCurHintTextColor && mText.length() == 0) {
            mCurHintTextColor = color;
            inval = true;
        }
    }
    if (inval) {
        // Text needs to be redrawn with the new color
        if (mEditor != null) mEditor.invalidateTextDisplayList();
        invalidate();
    }
}

setTextColor() 以 invalidate() 结束。

setBackgroundColor() 以 invalidate() 结束？或 .mutate()).setColor(color) ？或 applyBackgroundTint() ？

Answer 1

https://github.com/android/platform_frameworks_base/blob/master/graphics/java/android/graphics/Color.java

public static int rgb(int red, int green, int blue) {
    return (0xFF << 24) | (red << 16) | (green << 8) | blue;
}

对比

public static int parseColor(String colorString) {
    if (colorString.charAt(0) == '#') {
        // Use a long to avoid rollovers on #ffXXXXXX
        long color = Long.parseLong(colorString.substring(1), 16);
        if (colorString.length() == 7) {
            // Set the alpha value
            color |= 0x00000000ff000000;
        } else if (colorString.length() != 9) {
            throw new IllegalArgumentException("Unknown color");
        }
        return (int)color;
    } else {
        Integer color = sColorNameMap.get(colorString.toLowerCase(Locale.ROOT));
        if (color != null) {
            return color;
        }
    }
    throw new IllegalArgumentException("Unknown color");
}

我没有测量过，但我猜

Color.rgb(184, 134, 011));

速度更快，因为它使用简单的位移并且必须处理更小的输入集。

我认为在实践中这种差异最多可以忽略不计。